Concrete Block Calculator
Enter wall dimensions, pick block type, and get the exact number of CMU blocks, mortar bags, and installed cost — including openings subtraction.
Last updated: June 2026
Most common. Load-bearing walls, foundations, retaining walls.
Material & Cost Estimate
Price data sources: Inch Calculator CMU Guide · concreteblockcalculator.com · HomeAdvisor 2026 Masonry Cost · NCMA (National Concrete Masonry Association)
Last verified: June 2026
How the Math Works
Standard 8"×8"×16" CMU blocks (including 3/8" mortar joints) cover 0.889 square feet each. That means you need 1.125 blocks per square foot of wall.
Formula: blocks = (wall length × height − openings) × 1.125 × 1.05 (5% waste). The calculator handles this automatically — including rounding up to full blocks and calculating mortar.
CMU Block Types Compared
| Block Type | Nominal Size | $/block | Use |
|---|---|---|---|
| 6" CMU (Half-block) | 6"×8"×16" | $1.3-2.5 | Thinner wall, non-load-bearing partitions. Lighter weight. |
| 8" CMU (Standard) | 8"×8"×16" | $1.5-3 | Most common. Load-bearing walls, foundations, retaining walls. |
| 12" CMU (Heavy-duty) | 12"×8"×16" | $2.5-4.5 | Thickest standard. Structural walls, tall retaining walls, commercial. |
All standard CMU have the same face dimensions (8" tall × 16" long). The difference is wall thickness.
Cost Breakdown
| Component | % of Total | What it covers |
|---|---|---|
| Blocks (CMU) | 20-25% | Concrete masonry units, 8x8x16 standard |
| Mortar & rebar | 8-12% | Type S mortar, horizontal/vertical rebar, fill |
| Labor (mason + tender) | 50-60% | Skilled mason + helper, laying blocks, tooling joints |
| Equipment & overhead | 8-12% | Mixer, scaffolding, saw, trucking, contractor overhead |
How Location Affects Your Cost
| Region | Labor | Materials |
|---|---|---|
| Midwest | 1x | 1x |
| Southeast | 0.9x | 0.95x |
| Southwest | 1.05x | 1.1x |
| Northeast | 1.3x | 1.2x |
| West Coast | 1.4x | 1.25x |
To adjust: multiply the calculator's total by your region's average multiplier. Source: Remodeling Magazine 2026 Cost vs Value Report regional indexing + HomeAdvisor 2026 Regional Cost Index.
Masonry contractor? Price CMU walls faster.
JobTread tracks block counts, mortar quantities, rebar, and labor hours for masonry projects. Generate bids with accurate material takeoffs.
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Try JobTread FreeRed Flags in Contractor Quotes
We've reviewed hundreds of quotes. These are the warning signs that a contractor may cut corners or overcharge:
- Forgetting corner blocks: Outside corners need special corner blocks. Calculate one per linear foot of corner height.
- Underestimating waste: 5% minimum for pros, 10-15% for beginners who break more blocks.
- Not accounting for rebar and fill: Structural walls require vertical rebar and concrete grout fill in cores.
- Using wrong mortar type: Type S is standard for load-bearing walls. Type N is only for non-structural.
Common CMU Estimating Mistakes
Forgetting corner blocks: Standard blocks are flat-ended. Outside corners need special corner blocks (sold by the piece). Calculate 1 corner block per linear foot of outside corner height.
Underestimating waste: 5% waste is the minimum. Beginner masons break 10-15%. Buy extra blocks — running out mid-job costs more in delivery fees than the blocks themselves.
Not accounting for rebar/fill: Structural walls require vertical rebar in every other core, filled with concrete grout. This adds $2-$4/sq ft. The calculator doesn't include this — add it for structural projects.
Mortar shrinkage: Premixed Type S mortar yields about 70% of bag volume after water addition. Buy 10% extra for first-time DIYers who over-butter joints.
Frequently Asked Questions
How many concrete blocks do I need per square foot?
You need 1.125 standard 8"×8"×16" concrete blocks per square foot of wall. This accounts for the 3/8" mortar joint between blocks. Example: a 10'×8' wall (80 sq ft) needs 80 × 1.125 = 90 blocks. Always add 5% for waste and breakage — so 95 blocks for this wall. The calculator above does this automatically, including openings (doors/windows) subtraction.
How many concrete blocks are in a pallet?
A standard pallet holds 108 to 144 blocks, depending on block size and manufacturer. For 8"×8"×16" standard CMU: typically 108 per pallet (some suppliers pack 120 or 144). For 6" blocks: up to 144 per pallet. For 12" blocks: 72-90 per pallet. A pallet of 108 standard blocks weighs about 2,800-3,400 lbs (26-32 lbs per block). Always confirm pallet count with your supplier — it varies by region.
How much mortar do I need for concrete blocks?
You need approximately 3 bags of mortar (80 lb each) per 100 blocks laid. For a wall with 90 blocks, that's 3 bags. For 200 blocks, 6 bags. Each 80-lb bag of Type S mortar mix costs about $6-$8 and covers roughly 35 blocks at standard 3/8" joint thickness. Thicker mortar joints or filling block cores with grout increases mortar usage. The calculator above estimates mortar bags automatically based on block count.
How much does a concrete block wall cost per square foot?
A concrete block wall costs $10 to $20 per square foot installed in 2026, including materials and labor. Material-only cost runs $3-$6/sq ft (blocks + mortar + rebar). Labor is $8-$15/sq ft for a skilled mason crew. Standard 8" CMU costs $1.50-$3.00 per block. A 200 sq ft wall (20'×10') runs $2,000-$4,000 total. Retaining walls and structural walls cost more due to engineering requirements, rebar, and concrete fill.
How much does a single concrete block cost?
Standard 8"×8"×16" CMU costs $1.50-$3.00 per block at most building supply stores (2026). 6" blocks cost $1.30-$2.50. 12" blocks cost $2.50-$4.50. Bulk purchases (pallet pricing) save 10-20%. Specialty blocks (corner blocks, half-blocks, lintel blocks) cost 20-50% more. Prices vary by region — urban markets with multiple suppliers are cheaper than rural areas with limited supply.
Should I use concrete blocks or poured concrete for my wall?
For most residential walls under 8 feet, concrete blocks (CMU) are the standard choice — cheaper ($10-$20/sq ft), easier for small crews, and don't require formwork. Poured concrete walls cost $15-$30/sq ft but are stronger, more water-resistant, and faster for large walls (once forms are set). For foundations and retaining walls over 4 feet, many engineers recommend poured concrete for superior structural integrity. For garden walls and partitions under 4 feet, CMU is almost always the right choice.
Can I lay concrete blocks myself?
Laying CMU is DIY-possible for low walls (under 4 feet, non-structural) if you learn proper technique: buttering the head joint, leveling each course, maintaining consistent mortar joint thickness. A first-time DIYer can lay about 30-50 blocks per day vs 150-200 for a skilled mason. For structural walls, retaining walls, or anything requiring rebar/core fill, hire a licensed mason — improper installation causes catastrophic failures. Budget $1,500-$3,000 for a pro-installed 200 sq ft wall vs $500-$800 DIY (materials only).
How to paint concrete block walls?
For interior CMU: apply one coat of masonry primer ($30-$50/gallon, like Kilz Masonry) followed by two coats of 100% acrylic latex paint. For exterior: use elastomeric coating ($50-$80/gallon) which bridges hairline cracks and waterproofs. Always clean the wall first with TSP and let dry 24 hours. New block walls should cure 30 days before painting. Skip primer on bare masonry and the paint will peel within 2 years — concrete is highly alkaline (pH 12-13) and degrades standard paint binders. Coverage: 200-300 sq ft per gallon on rough block (less than on drywall). Total cost: $0.75-$1.50/sq ft DIY, $2-$4/sq ft professional.
How to waterproof a block wall from the outside?
Exterior waterproofing requires three layers: (1) masonry sealer applied to the wall surface (silane/siloxane, $40-$80/gallon), (2) dimple mat drainage board (like Delta-MS, $1-$2/sq ft) mechanically fastened over the sealer, (3) footer drain pipe (4-inch perforated PVC wrapped in fabric, $3-$5/linear ft) at the base carrying water to a sump or daylight. Install during excavation before backfill — retrofitting costs $50-$150/sq ft because you must dig out the foundation. Required for any block wall below grade (basements, retaining walls). Without proper exterior waterproofing, block walls leak at the mortar joints within 5-10 years.
Real Project Example
4 ft Retaining Wall — 8 in CMU
Salt Lake City, UT · 2026
Built an 8x4 ft concrete block retaining wall to level a sloped side yard for a garden bed.
How It Went Down
Trench and footing
Dug 18 in deep trench, poured 6 in concrete footing with rebar dowels
Frost line here is 30 in — footing below grade prevents heave. Skipped this on the neighbor's wall and it tilted in 2 winters
First course
Set first course level with 3/8 in mortar joints, checked every block with 4-ft level
Spent 90 minutes on the first course alone — everything above follows this baseline
Stacking and rebar
Stacked blocks with staggered joints, filled every other cell with rebar and concrete
Used 120 blocks total — the calculator said 112, we bought 10% extra and used 6 for cuts and breakage
Cap and waterproofing
Applied cap blocks, brushed on foundation waterproofing on the earth side
Waterproofing the back side cost $35 — prevents water infiltration that causes freeze-thaw spalling
What we learned: The 10% waste factor is non-negotiable. We broke 6 blocks trying to cut them with a rental wet saw — buying the exact count would have meant a second trip to the supply yard mid-job.
EstimatorSuite contractor interviews, 2026
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